Boiling exoplanet has titanium atmosphere

The exoplanet WASP-19b has huge amounts of titanium oxide in its atmosphere, causing the atmosphere to 'reverse' so some of the upper layers are warmer than those lower down.

An artist's impression showing the exoplanet WASP-19b, in which atmosphere astronomers detected titanium oxide for the first time. In large enough quantities, titanium oxide can prevent heat from entering or escaping an atmosphere, leading to a thermal inversion — the temperature is higher in the upper atmosphere and lower further down, the opposite of the normal situation.

The Very Large Telescope was able to measure information about the planet’s chemical composition, temperature and pressure structure. Image Credit: ESO/M Kornmesser

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The sky of a distant exoplanet is an inferno of titanium oxide, according to the latest images taken by ESO’s Very Large Telescope (VLT).

The find will help unravel not only the chemical composition of the planet, called WASP-19b, but the temperature and pressure structure of its atmosphere.

The distant planet is about the same mass as Jupiter, but is in a much tighter orbit so it orbits its star every 19 hours.

The close proximity to its star means that temperatures can reach as high as 2,000ºC. But this might not be the only thing affecting the planet’s temperature.

“The presence of titanium oxide in the atmosphere of WASP-19b can have substantial effects on the atmospheric temperature structure and circulation,” says Ryan MacDonald, part of the team behind the study, from the University of Cambridge.

Titanium oxide, a substance rarely found on Earth, acts as an absorber of heat.

If enough is present in an atmosphere, it can cause something known as thermal inversion, where heat is absorbed in the upper levels of the atmosphere, making them cooler than lower layers.

On Earth, the ozone layer plays a similar roll by causing inversion in the stratosphere.

Titanium oxide was detected by observing the starlight that came through the planet’s atmosphere and searching for the spectral fingerprints it left behind in the light.

When WASP-19b transits infront of its star, chemicals in the atmosphere scatter away certain frequencies of light. By carefully analysing the light, the team could deduce what molecules lie within the atmosphere Credit: ESO/M Kornmesser
When WASP-19b transits infront of its star, chemicals in the atmosphere scatter away certain frequencies of light. By carefully analysing the light, the team could deduce what molecules lie within the atmosphere
Credit: ESO/M Kornmesser

By analysing these signatures, the team were able to find small amounts of titanium oxide, water and traces of sodium alongside a scattering global haze.

“Detecting such molecules is, however, no simple feat,” says Elyar Sedaghati, who worked on the project for two years while a student at the European Southern Observatory.

“Not only do we need data of exceptional quality, but we also need to perform a sophisticated analysis.

“We used an algorithm that explores many millions of spectra spanning a wide range of chemical compositions, temperatures and cloud or haze properties in order to draw our conclusions,” adds Sedaghati.

The ability to find metal oxides will help future teams aiming to investigate the effect exoplanet atmospheres have on the worlds they surround.

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This could help gauge the habitability of planets around distant stars.